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Elon Musk has been at SpaceX's test site for its rocket engines in central Texas this weekend. The facility near McGregor is where the company both tests Merlin engines for Falcon 9 flights and also performs some experimental firings.

Due to a variety of reasons, including financial pressures, SpaceX is pushing hard on the development of its next-generation Super Heavy rocket and Starship spacecraft. This push was evidenced this weekend when, at 1:15am Central Time on Sunday morning, Musk shared a nighttime picture of himself on the test stand at McGregor, saying, "with engineering team getting ready to fire new Raptor rocket engine." It was the dead of night on Super Bowl weekend, and they were working on an engine that won't go into space for a few years. But that didn't matter.

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The test itself appears to have taken place later on Sunday. Eyewitness reports in Central Texas noted a large pop on Sunday evening, and more later Sunday night. Musk himself tweeted a photo shortly before 10pm local time, and thereafter a video. The test firing itself lasts for a few seconds, and was evidently successful. "First firing of Starship Raptor flight engine! So proud of great work by @SpaceX team!!" Musk wrote.

Engineers can do a lot of analysis on a rocket motor prior to putting it on a test stand, but there is no substitute for lighting the candle and seeing what happens. One of the most important things that rocket scientists will study during these early test firings is the color of the flame. In this case, the rocket engine's exhaust turns green toward the end of the test firing. This was likely due to a slight burning of copper liner from the engine chamber. It should not have burned, and fixing the problem will likely require adding more insulation. However, initial test firings are designed precisely to detect such issues and will ultimately lead to a better engine. Generally, any "first" test firing of a new, full-scale rocket engine that doesn't end in an uncontrolled explosion is a good thing.

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Musk and SpaceX have a lot riding on this engine, as it will power both the Super Heavy rocket during launch and the Starship spacecraft in space. This particular engine may end up as one of three engines used as part of the "hopper" tests of a Starship model later this spring, when the vehicle ascends into the lower atmosphere and then descends on its own power. The first launch of the rocket and Starship combined should come in the early 2020s.